1. Field of the Invention
The present invention relates generally to hoists, more particularly to hoists employing Weston-type load brakes, and most particularly to the provision of release mechanisms for such load brakes.
2. Description of the Prior Art
In the hoisting equipment industry, it is well known to provide Weston-type load brakes to hold a load during relaxation of the input force used to move the load. In a manually operated hoist, it is common to actuate the load brake through relative movement of a pair of rotatable input drive members, one of which drivingly engages a source of input force and the other of which engages a drive portion of the hoist. Problems in the use of such hoists are encountered when the hoist completes its lifting or lowering operation and the load is removed. The load brake maintains its engaged condition until a reverse torque is applied to the input drive members or until the mechanism is shock loaded to break its static frictional engagement effected by the input drive members during operation.
The former disengagement method is often impractical where the hoist is of the type suspended from a support during operation since there is nothing to restrain its motion responsive to reverse rotation in the absence of a load.
The latter method has the disadvantage of lacking control of input forces to the hoist which may result in overloading of parts of the hoist and damage thereto.